Incorporate lighting controls with BAS to save energy

Incorporating daylighting and lighting controls with a building automation system can result in energy savings.

Michael Chow and Julia Noschang, Metro CD Engineering, Powell, Ohio

09/24/2013

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Learning objectives

Understand the benefits of incorporating lighting, daylighting, and building automation systems.

Know the codes and standards that govern lighting and daylighting.

Learn to gather and analyze data from an automation system.

Incorporating daylighting and lighting controls with a building automation system (BAS) can result in significant energy savings. There are other benefits as well, including compliance with energy codes, U.S. Green Building Council (USGBC) LEED, credits, and Energy Star.

Building owners, architects, and engineers have embraced daylighting with the advent of LEED, ANSI/ASHRAE/IES Standard 90.1-2010 and the documented benefits of daylighting for the building occupants as well as energy savings. Energy Star’s website states research has shown that daylighting not only saves money, but also improves employee productivity and product sales.

According to AEP (American Electrical Power) Energy, integrating daylighting harvesting with lighting controls can reduce a building’s overall lighting energy usage by 20% to 90%. AEP has several case studies on its website showcasing these energy savings.

Daylight harvesting refers to controlling artificial lighting in response to daylight availability to maintain a consistent light level. As natural daylight enters a space, photocontrol sensors gauge the light level and through the lighting control system, artificial light levels are reduced. Conversely, when the sun sets or on a cloudy day, the sensor will gauge the light level and with the controls, artificial lighting levels are increased. The lighting controls should be programmed with delayed on/off settings to avoid nuisance fluctuations on windy days when shifting clouds cause variations in ambient lighting.

Strategies, benefits of integration

Most BAS vendors do not offer extensive packaged lighting controls. Typically, a separate lighting controller does this task. The BAS is a useful tool to passively monitor energy usage to provide the basis for lighting controls strategies. Due to the highly customizable nature of a BAS, the designer will need to develop detailed sequences of operation for lighting controls through a BAS. Dedicated lighting controls packages have all the sequencing generally pre-packaged with BAS monitoring dry contacts. Many manufacturers of lighting controllers have the ability to network to a BAS. Some BAS are now incorporating lighting controls directly into the BAS.

What are some of the strategies and benefits for integrating daylighting and lighting controls with a BAS, either directly or indirectly?

The BAS usually controls and monitors other systems, such as HVAC and energy monitoring systems. Incorporating lighting control systems allows the facility manager and technicians the ability to control and monitor the lighting systems.

Most BAS and lighting controller manufacturers allow their systems to be controlled and monitored remotely through dedicated software and/or a Web interface. Most systems comprise a lighting controller and a BAS that are not integrated. With these systems, remote access would involve two separate systems: one for the lighting controller and another for the BAS. The two would be connected through a network.

A BAS with integrated lighting controls simplifies training, maintenance, and operations through the use of one interface. However, few integrated systems are currently available and these systems may not have as robust lighting controls compared to stand-alone lighting controllers. Consideration should be given to reviewing the pros and cons of separate systems for the lighting controller and BAS versus an integrated system.

Integrating lighting and daylighting controls with a BAS requires coordination between the lighting engineer and the BAS design engineer. Open protocols such as BACnet, LonWorks, and Modbus enable products from different manufacturers to work together. Engineers should consider specifying daylighting and lighting control products that incorporate open protocols for future expansion and retrofits.

Coordinated scheduling of lighting and HVAC loads is a way to save considerable energy. Synergies in energy savings can exist between the lighting and HVAC systems with a BAS. For example, a BAS through an occupancy sensor’s monitoring of a space can open or close the damper of a variable air volume (VAV) terminal unit. A typical scenario involves the occupancy sensor turning on the lighting in an occupied space. This is then communicated to the BAS, typically through the lighting controller or through monitoring of contacts. The BAS then opens the VAV’s damper to provide the necessary amount of heating or cooling for occupant thermal comfort. Conversely, the BAS can save energy by closing a VAV’s damper when an occupancy sensor detects a space is no longer occupied and has turned off the lighting. A detailed sequence of operations should be provided by the designer to the controls contractor when coordinating the lighting and HVAC systems.

Most lighting controls manufacturers’ hardware allows the photocontrol sensors to interface directly with lighting fixtures. This enables the sensor to directly control the artificial lighting levels without having to go through a BAS. However, the BAS can monitor the energy consumption for these lighting circuits and use this information to determine energy savings.

Digital Addressable Lighting Interface (DALI) is a standard protocol (IEC 60929 and IEC 62386) that consists of a controller with lighting ballasts, occupancy sensors, and so on. The DALI controller can monitor and control each lighting fixture through wiring between the controller and devices or between devices. Depending upon the type of DALI system, the DALI controller may be able to network with a BAS. A potential energy and maintenance management tool can exist if the specified DALI controller is programmed to track the number of operating hours for each lighting fixture as well as the number of on/off cycles per fixture. This data can be used by maintenance personnel to perform relamping as it correlates to the lumen depreciation and mean life for the lamps in each lighting fixture. Energy savings can also be calculated based on the time the lighting fixtures are off.